Series capacitor banks are used to enhance both the steady state and dynamic power transmission capacity of overhead power transmission lines by compensating the inductive reactance of the line.
The use of a capacitor bank in series electrical connection (also interchangeably referred to herein as “electrical communication”) with the power transmission line makes the capacitor bank sensitive to the faults on the power transmission line. Various techniques are employed to protect the capacitor bank from an over-voltage condition. These techniques include use of a Metal Oxide Varistor, (MOV) which is susceptible to sustained overload conditions when the current and/or energy absorption exceeds its rated capacity. Traditionally, a non-conductive triggered (or triggerable) or untriggered gap switch that has a high voltage and a high current rating is connected in parallel with the MOV and the capacitor bank to withstand simultaneously a fault current in the power transmission line and discharge current from the capacitor bank, and also to quickly bypass both the MOV and the capacitor bank in order to limit the time that both are exposed to the system fault. Note that “triggering” refers to the act of turning a non-conductive gap into a gap that is conducting current effectively creating a fast closing switch that does not require overcoming the inertia of movable switch contacts. The non-conductive gap functions as a fast-bypass device for the MOV and the capacitor bank by providing a parallel circuit for the fault currents and simultaneously allowing the capacitor bank to safely discharge.
Traditional designs of this non-conductive gap combine the high-voltage dielectric withstand requirements of the non-triggered, non-conducting gap with the high-current fault plus discharge current requirements of the triggered, conducting gap into a single component capable of both sets of requirements. This combination of requirements into just one component may be expensive in terms of cost, complexity of design, and unreliability.
Accordingly, there is need for a reliable technique that can handle high voltage and high current overloads efficiently and economically. There is further a need for systems and methods for protecting a series capacitor bank.